Good standard bicycle tool is made by Parks Tools. It seems they have a monopoly on them.

A good torque wrench is the kind that clicks. you dial in the torque required. Tool will make a click sound when the desired torque is reached.

A cheaper version has a needle pointer with a scale near the handle.

Best to get the clicky kind. Quite a bit more expensive but so worth it. Ask you LBS to the size of the torque wrench you should buy. I probably would get a 1/4" ratchet first since most of the bicycle stuff is small.

other sources of good torque wrench are: Sears Craftsman, Snap-on (not sure where you would buy one of them). I would avoid the no name brand cheap chinese imports and stuff from Harbor Freight.

Correct tightness of bolts and nuts are very important on seat posts, stems etc.